Render scheduler-role health on the Waterline dashboard

Adds a Scheduler-role health section to the Operator metrics panel on
`resources/js/screens/dashboard.vue`. The section reads the frozen
`operator_metrics.schedules.*` namespace exposed by the workflow v2
package — `active`, `paused`, `missed`, `oldest_overdue_at`,
`max_overdue_ms`, `fires_total`, `failures_total` — so operators can
read namespace-wide scheduler lag and failure trends on the dashboard
without cross-referencing the schedules registry.

Graceful degradation: the section renders a short 'no scheduler-role
metrics exposed' note when the `operator_metrics.schedules` key is
absent (pre-alpha workflow builds that predate the schedule metrics
surface). The rest of the panel renders unchanged.

Assets: `public/app.js` + `public/mix-manifest.json` rebuilt with
`npm run production`.

Tests: V2DashboardStatsControllerTest 4/125 green under
phpunit-sqlite.xml in php:8.4-cli-alpine. Public Boundary scan exit 0.
No feature assertion is added for the `operator_metrics.schedules`
keys yet because the vendored workflow alpha predates the schedule
metrics contract; once a new alpha lands, a follow-up slice can pin
the key shape in V2DashboardStatsControllerTest.

Author: durable-workflow-ops

public/app.js

@@ -1,5 +1,5 @@
 {
-    "/app.js": "/app.js?id=9ffaca09c5284fe2234d8db01eaa8be7",
+    "/app.js": "/app.js?id=bd13ae38fe059a9a27f896bb0d995078",
     "/app-dark.css": "/app-dark.css?id=8b1b08a71c8e9860d0a9030d902c30d0",
     "/app.css": "/app.css?id=4d346e04fa466f5227cee3c313fbea25",
     "/img/favicon.png": "/img/favicon.png?id=7c006241b093796d6abfa3049df93a59",

public/mix-manifest.json

@@ -411,6 +411,28 @@
                             </p>
                         </section>
 
+                        <section class="wl-operator-section">
+                            <div class="wl-panel-subtitle">Scheduler-role health</div>
+                            <p v-if="!operatorSchedulesAvailable()" class="text-muted">
+                                No scheduler-role metrics exposed by the current workflow engine.
+                            </p>
+                            <template v-else>
+                                <p>
+                                    {{ operatorMetricLabel('schedules', 'active') }} active schedules,
+                                    {{ operatorMetricLabel('schedules', 'paused') }} paused,
+                                    {{ operatorMetricLabel('schedules', 'missed') }} overdue this tick,
+                                    oldest {{ operatorDurationMetricLabel('schedules', 'max_overdue_ms') }} behind.
+                                </p>
+                                <p v-if="operatorScheduleOldestOverdueAt()">
+                                    Oldest overdue fire due at {{ operatorScheduleOldestOverdueAt() }}.
+                                </p>
+                                <p>
+                                    {{ operatorMetricLabel('schedules', 'fires_total') }} fires recorded against active schedules,
+                                    {{ operatorMetricLabel('schedules', 'failures_total') }} failures.
+                                </p>
+                            </template>
+                        </section>
+
                         <section class="wl-operator-section">
                             <div class="wl-panel-subtitle">Worker compatibility fleet</div>
                             <p v-if="!operatorWorkerFleet().length" class="text-muted">
@@ -1070,6 +1092,18 @@ export default {
             return repair.oldest_missing_run_started_at || null;
         },
 
+        operatorSchedulesAvailable() {
+            const schedules = this.operatorMetrics && this.operatorMetrics.schedules;
+
+            return schedules !== undefined && schedules !== null;
+        },
+
+        operatorScheduleOldestOverdueAt() {
+            const schedules = (this.operatorMetrics && this.operatorMetrics.schedules) || {};
+
+            return schedules.oldest_overdue_at || null;
+        },
+
         operatorWorkerFleet() {
             const workers = (this.operatorMetrics && this.operatorMetrics.workers) || {};
             const fleet = Array.isArray(workers.fleet) ? workers.fleet : [];